Such a method is known in the art and is employed in the grain industry. This involves, for example, wheat being ground and thus being separated and washed, followed by the gluten fraction being separated from the starch fraction. The wet gluten mass is washed and compressed in preparation for the subsequent drying process, to obtain the desired dry gluten particles. Gluten is the general term for the proteins which are present in grain products, for example wheat. Gluten are added, for example, to bakery products, to cause them to rise. This characteristic is referred to by the term "vitality". It is the result of gluten having an elastic structure which can be expanded, for example by means of air or gas. In the wet state the vitality can be determined on the basis of the extent to which the gluten can be stretched without breaking under standardized conditions.
Vital gluten are separated from the starch in completely hydrated form. This form comprises fairly large balls--somewhat comparable to chewing gum--which need to be formed into a fine powder during drying. It is known in the art that the vitality is adversely affected by the mechanical shear forces, required for size reduction of the mass, and the drying temperature. So as not to impair the vitality of the wet gluten mass, the drying processes employed in practice need to be carried out gently. Indeed, existing drying systems are based on expansion-drying (flash-drying) at low temperature to minimize the effect of the temperature and to limit the residence time. In the process, the heat required for drying is abstracted from the product itself, so that the product is not exposed to a detrimental high temperature. Such drying, however, requires (very) small particles which can readily be dispersed in a stream of hot air in the drier. The small particles required are produced according to the prior art by the wet gluten mass first being made into a thin sheet (for example by extrusion through a slot-like orifice) or small granules and these then being fed into a hot airstream which is already transporting a large quantity of semidried and semipowdered vital gluten which are circulated in a drier which is provided with a disintegrator and within which the wet gluten, either in the form of a thin sheet or as granules, are converted into even smaller particles. The circulating, partly ground and partly dried particles are deposited on particles "freshly" introduced into the drier and thus form a layer thereon which ensures that the freshly introduced gluten will not, as a result of the moisture present therein, adhere to the walls and the like of the drier. A mixture thus formed passes through the drier and arrives at a classifying device, in which the finer and drier particles are separated from the coarser and wetter particles in the airstream. Finally, the separated gluten particles are subjected to a final filtering operation, in which the air is discharged to the atmosphere. As will be clear from the above, the remainder of the particles is returned to the drier feed.